This invention relates to a shock reducing suspension used with agricultural work vehicles for connecting an implement such as a sprayer boom assembly to the work vehicle.
Agricultural work vehicles such as sprayers and wind rowers typically comprise a work vehicle supported on wheels and to which is connected a working implement with provision for raising and lowering the implement relative to the ground and to the work vehicle. Typically this provision comprises generally parallel arm linkages which maintain the orientation of the implement relative to the work vehicle as it raised or lowered. Particular implements for use with a work vehicle may be a wind rower header or a sprayer boom assembly. These implements may have additional supports such as wheels to guide the height of the assembly above the ground or to make intermittent contact with the ground to prevent other components of the implement from contacting the ground, or they may have none at all. The implement may be fully suspended by the work vehicle. Hydraulic actuators are typically used for raising or lowering the implement. The actuators may be connected between the parallel arms, or between one of the parallel arms and either the work vehicle or the implement, or between the work vehicle and the implement.
The work vehicle may of the type adapted to be pulled by a pulling vehicle or may be self-propelled. The ground across which the work vehicle moves may be uneven, subjecting the work vehicle to sudden vertical components of movement. Sudden changes in movement of the work vehicle are transmitted to the implement through the parallel arm connection and result in shock forces between the work vehicle and implement through the parallel arm connection.
In an effort to reduce work time and increase efficiency, implements such as sprayer booms are generally being made longer to cover a wider area of ground in a single pass. As the boom length increases, so does the mass of the implement, and the resultant shock forces increase in proportion to that mass. Uncontrolled movement of the implement can also result in undesirable variations in the work being performed, for example, variations in spray pattern on a field from liquid spray nozzles mounted across a spray boom.
Prior attempts have been made to reduce the shock forces that result from sudden changes in movement such as those shown in U.S. Pat. Nos. 5,375,767 and 4,197,999. These patents show spray boom assemblies with parallel arm connections to a work vehicle in which springs and dampers are used to allow controlled movement between the work vehicle and implement and to reduce acceleration of the implement and minimize shock forces. However, these designs do not have convenient means to adjust the height of the spray boom relative to the work vehicle or relative to the ground.
Other known prior art designs known have hydraulic actuators used to control movement between a work vehicle and an implement connected to it by parallel arms. Some of these include hydraulic accumulators in the circuit in which the actuators are connected so that increased forces are absorbed by the accumulator.
Another prior design is used on machines made by Redball in which a hydraulic actuator is used to control movement between a work vehicle and spray boom connected to the work vehicle by parallel arms. In this design a suspension device is mounted to the work vehicle comprising of a rockshaft supported at both ends to the vehicle by torsional elastic joints as are disclosed in patents of Neidhart U.S. Pat. No. 2,712,742 or Henschen U.S. Pat. No. 5,411,287 and U.S. Pat. No. 3,436,069. An arm extends from the rockshaft and one end of the hydraulic actuator is connected to an end of the arm offset from the rotational axis of the rockshaft. The other end of the actuator is connected to the spray boom implement or to a parallel arm near one end, which is connected to the spray boom implement. Force from sudden changes to vertical movement of the implement act through the hydraulic actuator and arm to be absorbed by the elastic joints through rotation of the rockshaft.
It is desirable to provide a suspension system for agricultural work vehicle implements that allows for adjustment of the height of the implement, is effective at such various heights to reduce shock forces from sudden changes in vertical movement of the implement, and which is comparatively less expensive and less complicated than that of the prior art. It is desirable that such suspension system be easily incorporated into the boom lift linkage which supports the implement on the work vehicle.
A suspension system for supporting an implement on a work vehicle, in accordance with one aspect of the invention includes: a linkage mechanism adapted for pivotal connection between the work vehicle and the implement and adapted to pivot in such manner as to permit relative upward and downward movement between the vehicle and the implement while maintaining a controlled or selected orientation between them; a hydraulic actuator capable of extending and retracting and adapted to interact between the work vehicle and the implement when in use so as to effect the pivotal motion of said linkage and relative motion between the vehicle and implement in at least one direction; and a shock absorber adapted to be interposed between said hydraulic actuator and one of the work vehicle and the implement for absorbing shock loadings tending to pass between the vehicle and the implement via said hydraulic actuator when in use and regardless of the degree of extension or retraction of said actuator.
In another aspect the invention provides the combination of an agricultural work vehicle, an implement and a suspension system as recited above.
The shock absorber preferably includes a resilient cushion to absorb the shock loadings tending to be transmitted via said actuator.
The shock absorber also preferably includes an elongated link mounted for pivotal motion at a point between opposing ends thereof, one end portion of said elongated link being connected to an end of said actuator and the other end of said link being in a load transmitting relation to said resilient cushion whereby forces exerted by or on said actuator tend to effect pivotal motion of said elongated link and are transformed into compression forces on said resilient cushion.
The linkage mechanism preferably comprises upper and lower arm assemblies both of which have joints at their opposing ends to allow for pivotal connection thereof between the work vehicle and the implement. The elongated link of the shock absorber is also preferably mounted for said pivotal motion at a point which is co-axial with the joints at one end of one of said arm assemblies.
The suspension system advantageously includes mounting bracket securable to one of said implement and work vehicle and co-operating with the joints at said one end of said one of said arm assemblies to define a pivot axis therewith co-axial with the pivot axis of said elongated link. The mounting brackets preferably further define bearing surfaces with each said resilient cushion being interposed between a respective one of the bearing surfaces and a respective said other end of an associated said elongated link.
A further resilient cushion may be associated with another one of said bearing surfaces and said elongated link such that said shock absorber is capable of absorbing both compressive and tensile shock loadings passing through said hydraulic actuator. Each said resilient cushion is preferably of a resilient polyurethane material.
In a preferred form, said hydraulic actuator is connected in use between one of said arm assemblies and said one end portion of said elongated link of the shock absorber. The upper and lower arm assemblies may also be of equal length so as to form a parallel arm linkage system, said hydraulic actuator having one end thereof connected adjacent to an end portion of one of said arm assemblies while the other end of said actuator is connected to said one end portion of said elongated link.
These and other aspects of the invention will be accomplished by the instant invention by providing a suspension system for supporting an implement on a work vehicle. The suspension system includes a linkage mechanism providing pivotal connection between the work vehicle and the implement and adapted to pivot in such manner as to permit relative upward and downward movement between the vehicle and the implement while maintaining a controlled or selected orientation between them. A hydraulic actuator capable of extending and retracting is operatively connected between the work vehicle and the implement so as to effect the pivotal motion of said linkage and relative motion between the vehicle and implement. A shock absorber is interposed between the hydraulic actuator and one of the work vehicle and the implement for absorbing shock loadings tending to pass between the vehicle and the implement via said hydraulic actuator when in use. The shock absorber includes an elongated link mounted for pivotal motion at a point between opposing ends thereof. One end portion of the elongated link is connected to an end of the actuator and the other end of the link is in a load transmitting relation to a resilient cushion whereby forces exerted by or on said actuator tend to effect pivotal motion of the elongated link and are transformed into compression forces on the resilient cushion.